NEW ORLEANS, La. — As spring in the southern United States heralds the arrival of fledgling animal life, conservationists are anxiously watching the spread of a giant oil slick off the coast. More than 600 animal species are threatened by the slick, officials say.

“The wildlife nursery of North America is at risk,” warned Mark Floegel from Greenpeace USA.

Sea turtles and dolphins are especially vulnerable. “Dolphins are particularly in danger because they have no hair to protect them from the oil. The oil penetrates their eyes, their skin, and other mucous membranes,” said Mandy Tumlin, biologist at the Louisiana Department of Wildlife and Fisheries.

The turtle spotted by the NWF.Photo courtesy National Wildife FederationOn Tuesday a turtle was spotted swimming through the slick about 15 miles south of Louisiana by officials from the National Wildlife Federation. But nobody on board was trained in animal rescue and they were forced to leave the distressed turtle in the slick and simply report the coordinates to a hotline.

“It was very upsetting,” said Karla Raettig, NWF’s national campaign manager for coastal Louisiana.

With the accident coinciding with the arrival of spring, the region’s rich flora and fauna could be particularly at risk at a vulnerable stage in the life cycle.

“Birds migrate in the springtime. Right now, you’ve got the brown pelican nesting. He should be hatching soon. Other species are to follow,” said Michael Carloss from the Louisiana Department of Wildlife and Fisheries.

An oil-smeared brown pelican.Photo courtesy International Bird Rescue Research CenterOne brown pelican smeared in oil has already been captured, and it will not be the last, with an estimated 30,000 such birds in the state.

“Once the oil gets in the food chain, it infects the fishes. Then it transfers to the birds who transfer it to their young,” said Carloss.

Ingested oil can be deadly for digestive systems, causing infections and internal lesions which can be fatal, said Tumlin. And other fish-eaters lurking in the famous bayous could also be at risk, such as the alligators.

The stress of being mired in oil is another factor that could compromise the region’s birds.

“When the bird is stuck in an oil slick, it works a lot more to [get out of it]. Now if it manages to get out, its ability to fly will be reduced and it’ll be confused,” Carloss said. “And then you’ve got the young. We’re in the middle of nesting. If their parents die, they have no one to rely on to get fed and they die too.”

One of the species most at risk is believed to be the Kemp turtle, already facing extinction, and only found on the American continent. “The oil slick is right in the middle of their [migration] path. They’re currently migrating down to Mexico to lay their eggs,” said Sarah Burnette from the New Orleans Audubon Institute.

She estimated that about 20 dead turtles had already washed up on Mississippi beaches, but was not sure whether the oil slick was to blame.

But for Larry Schweiger of the National Wildlife Federation, the question raised by the oil slick is “not if there’s going to be problems with wildlife, it’s when.”

“You can’t put that much oil into an ecosystem and not have a major impact,” he warned.